Coke is a necessary ingredient in the production of steel. Specifically, coke acts as the fuel source in the blast furnaces used to produce steel.
Coke is manufactured by heating coal to a very high temperature. Conventionally, the heating occurs either in a by-product type oven, a non-recovery type oven, or a heat recovery type oven.
The by-product type oven and the non-recovery and heat recovery type ovens are distinguishable from each other operationally and structurally. In the by-product type oven, the by-products of the coking process are used in other processes in an attempt to maximize the efficiency of the coking process. In the non-recovery and heat recovery type ovens, as the name suggests, no attempt is made to recover the chemical by-products of the coking process. In the heat recovery type oven, the waste gases generated during the non-recovery carbonization process are used to generate steam, which in turn is used generally to generate electricity. In the by-product type oven, the coal is loaded from the top, and the product is removed by pushing the coke out of one of the sides. In the non-recovery and heat recovery type ovens, generally the oven is charged either through single or multiple openings and discharged through a single opening. Unless otherwise indicated, the term “non-recovery type oven” as used herein includes heat recovery type ovens.
All of these ovens usually have a non-uniform coal bulk density after initially charging the oven. Also, the removal of the coke from all of these ovens usually involves an elevation change, which can result in breakage. As a consequence, more of the coke oxidizes, decreasing yield and increasing emissions. This breakage results in a relatively unknown amount of coke surface area being exposed during the quenching process which follows the coking process. It is thus difficult to estimate the required amount and location of quenching material to be applied and the appropriate location to which the quenching material should be applied. Consequently, the moisture content of the coal is quite variable. Uniquely the coal and coke bed in non-recovery and heat-recovery ovens are exposed to oxidizing atmosphere which can decrease the coke yield; however, the drop in yield may be partially offset by carbon deposition.